Blundering airlines allowed a thief to snatch $1.6 million worth of banknotes from a diplomatic locker left unguarded on the tarmac, it was alleged yesterday.

The cash went missing at Auckland airport after an Air New Zealand jet transported it from Hong Kong, the High Court was told.

A communications mix-up alerted an opportunist, most likely a ground worker, to the money's arrival, it was claimed.

He or she made off with the cash and was never caught.

Hang Seng Bank Limited and the Bank of New Zealand are suing Cathay Pacific and Air New Zealand for the value of the banknotes, survey fees and damages arising from the theft nine years ago.

The thief found out the cash - NZ$300,000 in NZ$1 notes - was on its way after a telex was mistakenly sent to Air New Zealand's general staff office instead of its security office, barrister Clifford Smith, representing the banks, said.

The cargo clerk who received the message was said to have left work early for a medical appointment without notifying anyone.

'The key to the diplomatic box was left on a hook in the operations room in the airport where it could be, and was, taken and used to remove the bank notes,' Mr Smith said.

'It was stolen by somebody who was most likely to be acting in the scope of his employment at Air New Zealand.' Mr Smith attributed the theft to recklessness, beginning with Cathay's failure to send appropriate telexes, compounded by failures of Air New Zealand staff.

Cathay was responsible for ensuring the bills travelled safely to Auckland, where they were destined for the Bank of New Zealand.

The Hong Kong airline hired an Air New Zealand jet to transport the money on April 26, 1988. The notes were locked in a metal box, which was placed in a diplomatic locker inside the plane.

The jet touched down in the early hours of April 27.

But when the locker was opened five hours later, the money had vanished.

Air New Zealand staff pointed the finger at Cathay by claiming the money had not been put on the flight.

If true, this would be 'tantamount to a conspiracy among the members of Cathay's own loading team', Mr Smith said. 'Then we'd have a rock-solid case against Cathay Pacific.' But he said it was unlikely.